1996 Vol. 2, No. 4

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THE FRACTAL STRUCTUR FEATURES OF THE ACTIVE FAULTS IN THE UPPER REACHES OF THE QINGJIANG RIVER, AND THE ADJACENT REGIONS WESTERN HUBEI
Wang Huabin
1996, 2(4): 1-6.
Abstract (150) PDF (236KB)(13)
Abstract:
The fractal structure feactures of the active faults in the upper reaches of the Qingjing River and the adjacent regions western Hubei are analyzed.It is shown that the magnitude of the fractal dimension of a single fault reflects the complexity of the structure of fault, the stage of its development and activity, while those of a small region reflects the differential movement of the faults of various regions reflects the differential movement of the faults of various regions.At the same time, the relation between the fractal dimension of an active fault and its activity is studied.Its value can be regarded as a quantitative measure.
ON THE CHARACTERISTICS OF NEOTECTONIC ACTIVITIES IN BAIKAL RIFT SYSTEM
Yi Mingchu
1996, 2(4): 7-14.
Abstract (158) PDF (348KB)(8)
Abstract:
The history of faulting of the Baikal rift system is esentially coincident with the associated sedimentary processes.The evolution of the rift system can be broadly divided into two stages:Primary stage ranging in age from middle-late Eocene to early Pliocene (E22-3-N21)and main stage from middle late pliocene to Quaternary(N22-3-Q). The former is characterized by plastic deformation with no significant relief and weak fault activity, while the latter by brittle deformation with sharp relief and strong fault activity.
The Baikal depression is the earlist and the largest undewater depression of the Baikal rift system, where occurred notable neotectonic activities with an vertical movement from southwest to north-east.There are indications of a broadtilting from the west to the east in the area and the surrouding block mountains and basins.There have occurred bending and doming of a large number of planation surfaces and alluvialpluvial fans.The combination of different trend and mechanical properties suggests a NE-SW compression.
PRELIMINARY STUDY ON THE LATEST TECTONIC DEFORMATIONS ALONG NORTHEAST MARGIN OF THE QINGHAI-TIBETAN PLATEAU
Dai Huaguang, Jia Yunhong, Su Xiangzhou, Chen Yongming, Liu Hongchun, Hou Kangming
1996, 2(4): 15-20.
Abstract (196) PDF (265KB)(16)
Abstract:
A recently active tectonic system which strikes NNW is determined by analyzing and Studying the earthquakes, seismic deformation bands and active fault zones along the northeastern margin of the Qinghai-Tibetan Plateau. It consists mainly of a series of modern uplifts alternating with sudsidence zones. The latest tectonic deformation along the north-eastern margin of the plateau was found to have resulted from the activity of the system. In addition, a more detailed discussion of the deformation of the system and the earthquake-prone areas is made.
CENOZOIC EXTENSIONAL TECTONIC SYSTEM CONTROL OF THE UNDERGROUND WATER IN ORDOVICIAN LIMESTONE IN EAST WEIBEI, SHAANXI PROVINCE
Chen Changyan, Wang Sijing, Wang Guirong, Hang Kexing
1996, 2(4): 21-30.
Abstract (162) PDF (446KB)(10)
Abstract:
From the tectonic view point of a new mobilist and systematist, the model of Cenozoic extensional tectonic system distributed in east Weibei(eastern part of the northern Weihe River area, Shaanxi) is established in this paper. And the structural network control of the distribution of ordovician limestone, the hydrogeologic unit boundary and the movement of the underground water in the Ordovician limestone is discussed at some length with the texture and structure of the rockmass as a basis.
ORE-CONTROLLING STRUCTURES IN GAOLONG GOLD ORE DEPOSIT, NORTH-WESTERN GUANGXI PROVINCE
Yan Shouxun, Meng Xiangang
1996, 2(4): 31-35.
Abstract (176) PDF (224KB)(16)
Abstract:
The Gaolong dome is a fault-block dome rather than a short-axis anticline. The N-S-trending faults which the gold mineraliszed and silicified breccia zone are controlled are typical adjustment faults. The Gaolong block dome together with the surrouding NW trending faults and N-S-trending adjustment faults forms the ore-controlling system.
GRAIN SIZE DISTRIBUTION OF THE GOUGE FROM THE YUANYANGZHEN-FENGHUANGSHAN FAULT AND ITS ACTIVITY
Shao Shunmei, Zou Jinchang, Teng Ruizeng, Rong Dailu
1996, 2(4): 36-42.
Abstract (215) PDF (279KB)(9)
Abstract:
An investigation is made of the relation between the grain size distribution of gouge and fault activity. The gouge was taken from the Yuanyangzhen-Fenghuangshan fault of the northern marginal fault zone of the Western Qinling Mountain. The results show that the fault is characterized essentially by stick slip, with some steady-state creep. The activity of the fault is also discussied.
A STUDY ON THE DEFORMATION MECHANISM OF THE INCOMPETENT BEDS IN THE SHUIBUYA DAM SITE IN QINGJIANG RIVER
Jian Wenxing, Wu Shuren, Xu Ruichun
1996, 2(4): 43-48.
Abstract (188) PDF (322KB)(13)
Abstract:
The deformation mechanism of incompetent beds in the Shuibuya dam site may be summarized as follows:(1)The difference in composition and structure of the incompetent beds resulting from differential sedimentation determines essentilly their strength. (2)The deformation of soft sediments may facilitate their repeated shearsliding giving rise to the argillation, foliation and crenulation of the soft materials, and the flattening, rounding and rotation of the hard ones.
THE P-T PATH OF FORMATION AND EVOLUTION OF MENGZHONG ECLOGITE,DONGHAI,JIANGSU
Chen Xuanhua, Wang Xiaofeng, Chen Zhengle, Zhang Qing
1996, 2(4): 49-54.
Abstract (155) PDF (262KB)(7)
Abstract:
The exsolution of garnet out of Al2O3-rich clinopyroxene in the Mengzhong eclogite in Donghai, Jiangsu Province is studied.By an estimate of the pressure and temperature at which the mineral assemblages have developed during the various stages using geothermo-barometry, the P-T path is reconstructed for the formation and evolution of the eclogite.The result shows that it has undergone three stages of evolution:(1)The formaton of eclogite at mantle condition through the exsolution of garnet out of Al2O3-rich clinopyroxene due to the possible increasing of pressure and decreasing of temperature;(2)Tectonic emplacement of eclogite into the high amphibolite facies gneiss basement;(3)Retrograde metamorphism together with country rocks after the emplacement.
A STUDY ON THE BALANCED SECTION OF YANSHAN AREA
Yang Nong, Chen Zhengle, Xu Shunshan
1996, 2(4): 55-60.
Abstract (183) PDF (294KB)(7)
Abstract:
Based on the detailed study of the regional geological setting as well as the supracrustal structure in the Yanshan area, we have shown what should be followed in calculating the balanced section of the Mesozoic deformation and determined the main decollement surfaces.Three main balanced sections have been constructed.The results are checked by various data of strain measurements.As a result, we have a shortening of 27.9% of the Yanshan orogen during the Indosinian and 10.9% during the Yanshan Movement of the giving a more accurate description of the Mesozoic deformational features of the area.
THE DEFORMATION MECHANISM OF MARBLE MYLONITESIN THE DASHANKOU SHEAR ZONE
Yin Xiulan
1996, 2(4): 61-67.
Abstract (173) PDF (318KB)(8)
Abstract:
The Dashankou Ductile Shear Zone (DDSZ) is a typical example of strike slip ductile shear zone with in the crystal line axis of the Dabei orogenic belt parallel to its extension.The marble mylonites of which show a variety of microstructures usually occurring under greenschist facies conditions, such as mortar structure, mica fish, subgrain, S-C structure, asymmetric strain shadow and mineral crystal preferred orientation.The mylonitization is characterized by decreasing grain-size of calcits.Based on a large number of microstructures along with macroscopic kinematic characteristics, It is shown that the DDSZ is a dextral strike-slip ductile shear zone, which was modified by a low-angle ductile shear zone.From the deformed mineral assemblages, microstructures and fluid inclusions thermometry, the DDSZ was determined to have formed at a temperature of 350-450℃, and a pressure of 364-468 MPa with a differential stress of 30-130 MPa, a shear strain of 6.06-7.02, and a strain rate of 2.87×10-14 1 29×10-10 s-1, and a shear strain rate of 1.17×10-13-2.23×10-10 S-1, and the corresponding displacement rate being 25 30 mm/a.From an analysis of macrostructural, microstructural and petrologic data, it is inferred that the Dashankou dextral strike-slip ductile shear zone may be the result of an oblique collision between the North China craton and Yangtze craton during the Indosinian-Yanshanian orogenies.
A PRELIMINARY ANALYSIS OF THE MODEL OF OIL CONTROL FOR LISTRIC FAULTS
Sun Baoshan
1996, 2(4): 68-72.
Abstract (124) PDF (223KB)(11)
Abstract:
In this Paper, an analysis is made of the change of geological behaviours of faults during the change of their mechanical properties, with the Luntai listric fault in the northern Tarim Basin which was first a thrust fault and converted later into a normal fault as an example.It acted as a passageway for oil and gas when it was converted from a shear fault into a tensile fault, and conversely as a seal to block off oil and gas when it turned from a tensile fault to shear fault, and the associated rollover anticline may become an oil trap.The proposed oil-control model as indicated by oil-gas preservation in sediments overlying a fault may also be applicable to those in eastern China.
BRIEF NOTE ON THE APPLICATION OF X-RAY DETERMINATION OF PETROFABRICS TO STRUCTURAL ANALYSIS
Chen Bailin, Liu Zhaoxia
1996, 2(4): 73-79.
Abstract (207) PDF (339KB)(8)
Abstract:
In this paper, the authors first describe the characteristics of x-ray determination of petrofabrics and selection of the samples, and proceed to discuss the relation of quartz fabric to the deformation of rocks and of the quartz grains themselves.After demonstrating how to transform quartz(1010) polar digrams to the sketch of quartz optic axis, an example is taken to illustrate that a combination of x-ray determination with other microstructural analysis or fabric study will yield more information for the research of geological structures.
DISCUSSION ON THE REGIONAL STRUCTURAL FEATURES OF JIANGHAN BASIN SINCE THE INDOSINIAN MOVEMENT
Dai Shaowu
1996, 2(4): 80-84.
Abstract (197) PDF (249KB)(15)
Abstract:
Since the Indosinian movement there have developed in the Jianghan basin some specific structural types, such as the large folds and nappes by thrust faulting, fault blocks by extension, and the temporal and spatial transform structures by structural compounding.There also occur modification of Pre-Indosinian structures.
BIOMIGRATION,MARINE TRANSGRESSION AND GEOMECHANICS
Xu Bingchuan
1996, 2(4): 85-89.
Abstract (193) PDF (206KB)(6)
Abstract:
The development of palaeobiology has involved 4 stages:palaeomorphology, palaeoecology, palaeobiogeography and study of palaeobiomigration.The last stage is an inevitable outcome of the evolution of palaeobiology at the present time.J.S.Lee, founder of Geomechanics in China, had noted biomigration as early as 1920s, and applied it to study the rules governing marine transgression.In 1960s he further emphasized the significance of study of biomigration.It is thought that the study of palaeobiomigration may provide some important informations for the study of crustal movement as well as palaeobiology.
1996, 2(4): 90-91.
Abstract (93) PDF (85KB)(9)
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1996, 2(4): 92-93.
Abstract (153) PDF (82KB)(6)
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